There are a few posts on the forums discussing the benefits of amd64 versus x86.
They usually boil down to this: AMD64 can use more than 4GB and the advanced features
of the processor, while the apps under x86 are better.

In my case, I have a Core 2 CPU and 3GB RAM. It doesn't take too much
before Firefox and Chrome start chewing up more than a Gig each and the system
starts swapping.

Yeah, well I have a lot of tabs open. A typical situation is two firefox windows open,
one with 9 tabs, the other with five. And also a chrome session with five tabs open.
Looking at "top" shows Firefox and Chrome using more than a gig each.

What else is running and using space you ask? Gnome uses a bit. Nautilus is using more than
500 mb.

I am a pretty typical user, surfing the net. No gaming and so on.
So I think it is a relevant question.

The cache in preferences->advanced->network seems to refer to disk space,
not RAM, so I wonder if that would affect things. In any event, it is limited to 1024 MB
and is at the present time using 93 MB. So that isn't a huge problem.
But limiting it to zero..would that mean that every image has to be downloaded every time
a page is loaded?

Last time I've seen some measurements, amd64 uses about 25-30% more ram than the same apps running on a 32bit system. That said, your ram usage doesn't look ok. I can't imagine even on a 64bit install that Firefox would be using a gig. I'm on 32bit and top currently shows Firefox using 139MB of resident memory.

Oh, and about that "64bit had address more than 4GB of ram" thing? Well, on a 32bit install, even the 2GB I have are total overkill. So if that's the big advantage of 64bit, I can do without it. Which also saves me from needing certain libraries duplicated. There is one real advantage - x264 encoding is 10-15% faster on 64bit. But even that I can do without. Sorry for the mini-rant.

Well, that's why I'm asking. What do you think could be causing Firefox to use so much memory?

Exactly how much memory are firefox and chrome using? In cases where 6+ tabs are being used chrome actually ends up using more RAM and CPU than firefox due to the sandboxing and having each tab and extension as a new process so high memory usage isn't exactly unheard of, there are a bunch of benchmarks around. Make sure your firefox is up to date also, the developers have put a lot more work into reducing memory usage recently.

If there is actually a problem, it may be a firefox extension producing memory leaks.

VIRT stands for the virtual size of a process, which is the sum of memory it is actually using, memory it has mapped into itself (for instance the video card's RAM for the X server), files on disk that have been mapped into it (most notably shared libraries), and memory shared with other processes. VIRT represents how much memory the program is able to access at the present moment. RES stands for the resident size, which is an accurate representation of how much actual physical memory a process is consuming. (This also corresponds directly to the %MEM column.) This will virtually always be less than the VIRT size, since most programs depend on the C library.

200 megs or so of physical RAM being used by FF is honestly pretty normal if you have a few extensions and a few tabs, I suggest upgrading to FF8 to make sure you've got the latest update since as aforementioned mozilla has been working on reducing memory usage heavily.

I still have a older x86 rig that I use on occasion. I also have a nice shiny new amd64 bit rig. My old rig has a AMD 2500+ CPU, 2Gbs of ram and runs KDE 4.7.*. My new rig is a AMD Phenom 3.2Ghz X4 CPU with 16Gbs of ram and also runs KDE 4.7.* as well. It's in my sig below too I think. I wouldn't go as far to say double the ram but I have noticed it does use a good bit more on amd64. I read where someone said about 20 to 30% and I wouldn't disagree with that tho it could be a bit more in certain cases. I think mine uses a little more than that is why I say that but it could depend on a lot of variables too.

One thing I have also noticed, things seem to use more memory where there is more available. With me having 16Gbs of ram on the new rig, maybe it just saves a bit more since there is plenty of room.

I have not specifically measured this with the exact same versions of software and the exact same tabs open but I do keep both fairly up to date and frequent the same sites regularly. I may be a little off here and there but should be pretty close, even tho I don't work for any government.

I can't imagine even on a 64bit install that Firefox would be using a gig.

It depends on the web page, I have seen several fark.com threads crash browsers on computers with less than 2GB of ram. It got common enough it led to a redesign of how many threads are displayed by default on fark.

I can't imagine even on a 64bit install that Firefox would be using a gig.

It depends on the web page, I have seen several fark.com threads crash browsers on computers with less than 2GB of ram. It got common enough it led to a redesign of how many threads are displayed by default on fark.

I don't know what's happened there but you've somehow quoted me with something Gusar said that I didn't.. lol :p

It depends on the web page, I have seen several fark.com threads crash browsers on computers with less than 2GB of ram. It got common enough it led to a redesign of how many threads are displayed by default on fark.

I agree. I mostly use Seamonkey but also have Firefox. If I have been watching movies or something that use flash, java etc then Seamonkey or Firefox uses a good bit of ram. I have seen mine approach a Gb but usually close then reopen to clear out some. Having lots of tabs open really causes this. I try to limit my number of open tabs when I can.

I think the problem may not be the browser itself but some plugins and such that are used. I know my local weather radar makes it go up a good bit sometimes and I have to close the browser to make it turn the ram loose. It uses java since it shows the storms in motion and such.

Is it the Virtual memory or the Resident size that is relevant to performance?

The only place I know that describes the differences is in

Code:

man top

and scroll down to section 2. This is a snippet of what it says:

Quote:

n: %MEM -- Memory usage (RES)
A task's currently used share of available physical memory.

o: VIRT -- Virtual Image (kb)
The total amount of virtual memory used by the task. It includes all code, data and shared libraries plus pages that have been swapped out and
pages that have been mapped but not used.

p: SWAP -- Swapped size (kb)
Memory that is not resident but is present in a task. This is memory that has been swapped out but could include additional non-resident mem‐
ory. This column is calculated by subtracting physical memory from virtual memory.

I am noticing that for many processes, the Virtual size is five to ten times the size
of the Resident size. So this raises some questions.

Can I think of the Virtual size like a hotel or rental car company that is
placing a hold on my credit card? The amount hasn't been used (yet),
but no one else can use it either? What happens if another process comes along
and needs some space?

I am noticing that for many processes, the Virtual size is five to ten times the size
of the Resident size. So this raises some questions.

Can I think of the Virtual size like a hotel or rental car company that is
placing a hold on my credit card? The amount hasn't been used (yet),
but no one else can use it either? What happens if another process comes along
and needs some space?

No, it's not like a hold on your credit card. If you want to follow that analogy, and it's a bit strained, it's like cash you put in the bank 'cos you have enough in your wallet.

Virtual memory technology dates back to the late 1960's, when core memory was phenomenally expensive (though still cheaper than the CPU registers). Experiments showed that at any one time most programs only referenced about 1/3rd of the total memory they had allocated. That 1/3rd would change over the course of the program's execution - initialization typically has loads of definitions and parameters and files to process, creating various data structures; the main operation then uses only those tables, and perhaps some other files; occasionally, something unusual happens and some exception code runs, and accesses new stuff.

Now the other problem in those days was keeping that expensive CPU busy; a program would often wait for disk I/O or user input, so the system builders realized you needed more programs ready to run, so you could switch to another while waiting. If you moved the unused 2/3rd of a program's memory to disk, you could use it for another program. So in general, a 1Mb memory could hold the active memory for about 3Mb of programs. (Actually, even 1Mb was a lot then, a big computer was anything above 128 Kb.)

You say you're seeing rations of virtual:resident of 5:1. That's high, but you're probably including the daemon tasks that only wake up once every few seconds to take a few checks and then go back to sleep; they tend to have almost no resident code. The system automatically tends to keep the relevant memory residnet, provided you've enough RAM. If you don't, you get "thrashing", where the system keeps robbing one active task for memory for the next axtive task. That's called "overcommitting" memory, and the cure is to either run fewer programs, or to force memory hogs to use less (for example, a program may reserve a large amount for a lookup table, and then scatter a few entries thinly across it; a smaller table would just use it more efficiently), if they are configurable.

As to which of virtual or resident memory has most effect on performance, the answer is neither. Provided your system isn't overcommitted, you should barely notice the difference. If it is overcommitted, it's the ratio of the total memory being actually referenced by the active tasks to the total available RAM in your computer._________________Greybeard

If your system is overcommitted, it has to keep moving pages from RAM to disk. You can see this in vmstat output, where the "SO" column is the average rate at which the system swapped out pages during the last period. Note that the first line contains average data for all time. For example, the display below shows that overall, my system has been swapping about 10 pages/second, but over the four 10 second periods it ran, there was no swap out activity.

Your next question will be "how much paging is too much". I'm not sure; in part it will be affected by how may I/O operations your hardware can support. In some respects, it's swapping in that's bad, as that causes the process to wait until the swap completes, but the purpose of swapping out is to make space for swapping in another page. So on that basis, any swap activity is bad. But the occasional swap is little problem; a constant level of swap of a few per second is probably OK. I'd guess single disk systems will grind to a halt at something like 50/sec but that is a guess.

The question after that is "which process is causing the swapping". Sorry, I've not yet worked out how to answer that!_________________Greybeard

and I have the subjective impression that it is a lot easier on RAM and CPU than firefox - but I never really checked in a compareable way? Anyone with the same feelings?_________________Nothing is easier than being busy - and nothing more difficult than being effective.